The invention relates to data storage disk drives and in particular to latching a read/write arm that moves a read/write head over the surface of a magnetic data storage disk.
Magnetic disk drives for data storage are an integral part of almost all computers. A conventional magnetic disk drive comprises at least one magnetic data disk on which data bits can be recorded by changing the state of magnetic domains on the surface of the disk. The disk drive also comprises a read/write head, hereinafter referred to as a xe2x80x9cdata headxe2x80x9d for each of the at least one disk for xe2x80x9cwritingxe2x80x9d or xe2x80x9creadingxe2x80x9d the domains on the disk surface. The data head for a disk is located at one end of a read/write arm, hereinafter referred to as a xe2x80x9cdrive armxe2x80x9d. A drive arm motor moves the drive arm so as to accurately position the data head over different regions of the surface of the disk used for data storage in order to read or write data to these regions. The disk drive comprises a drive frame to which the at least one data disk, drive arm and other parts of the disk drive are mounted.
When in use, the disk is rotated at high speed by a spindle motor. The rotation causes a cushion of air to form between the data head and the disk surface that keeps the data head a small (generally less than a micron), substantially constant, distance from the disk surface. The air cushion thereby prevents direct and possibly damaging contact between the data head and the surface of the disk while the data head moves over the surface of the disk. In effect, the data head glides xe2x80x9cfrictionlessxe2x80x9d over the surface of the disk on an air bearing.
When not in use the disk is stationary and the drive arm is rotated into a parking position so that the data head is positioned away from regions of the surface of the disk that are used for data storage. The drive arm is secured in the parking position by a latching device. The latching device prevents an external shock or blow delivered to the disk drive from dislodging the drive arm from the parking position and causing the data head to come into contact with the disk surface while the disk is stationary.
Among prior art latching devices, hereafter referred to as xe2x80x9clatchesxe2x80x9d, used to secure a drive arm in a parking position are solenoid latches, magnetic capture latches, inertial latches and vane latches.
Solenoid latches use a solenoid or coil to produce a magnetic field that moves a locking pin or locking arm so as to engage and immobilize a drive arm in a parking position. Solenoid latches are often complicated, large and heavy, and their solenoids or coils must generally be shielded or distanced from the drive arm to prevent the magnetic fields of the solenoids or coils from affecting the operation of the drive arm motor.
Magnetic capture latches use a small permanent magnet and a strike plate formed from a ferromagnetic material to secure a drive arm in a parking position. Either one of the magnet or strike plate, is mounted on the drive arm and the other is mounted to the drive frame. When the drive arm enters the parking position the permanent magnet and strike plate come into contact and held together by the force of magnetic attraction between them. The drive arm is released from the parking position when the motor that moves the drive arm exerts sufficient force to pull the magnet and strike plate apart. Magnetic capture latches are often unreliable and release when the disk drive is subjected to a shock or blow that results in a force to the latch greater than the magnetic force binding the magnet and latch plate. Furthermore, the magnet must often be shielded to prevent its magnetic field from interfering with the motion of the drive arm. Also, the drive arm motor must be able to pull the magnet and strike plate apart in order to release the drive arm from the parking position. As a result, disk drives using magnetic capture latches often require drive arm motors that are stronger and heavier than drive arm motors used in disk drives operated with other types of latching devices.
An inertial latch uses the inertia of a drive arm and a locking element of the inertial latch to prevent the drive arm from dislodging from a parking position. When a shock or blow is delivered to a disk drive fitted with an inertial latch, the inertia of the locking element and drive arm cause the locking element and drive arm to move relative to each other in such a way that the locking element engages the drive arm and prevents the drive arm from leaving the parking position. Many inertial latches are unreliable and suffer from the fact that for certain directions of a shock or blow delivered to the disk drive, the inertial latch does not move so as to engage the drive arm.
With a vane latch, a drive arm is secured in a parking position by an air vane. The air vane is a thin generally rectangular sheet of material having two large planar surfaces. It is mounted in a disk drive close to and over a data disk of the disk drive with the large planar surfaces parallel to the plane of the data disk. When the drive arm is in the parking position a hole in the air vane engages a protuberance on the drive arm, thereby locking the drive arm in the parking position. When the disk rotates, air between the air vane and the disk is accelerated causing a Bernoulli effect to draw the air vane towards the disk and displace the hole in the air vane from the protuberance on the drive arm. The drive arm is thereby released from the parking position. Air vanes used in air vane latches are often large and air vane latches used in disk drives having multiple disks generally require more space between the disks than would be required using other types of latches. As a result, a disk drive using a vane latch must often be made larger and heavier than disk drives using other types of latches.
It would be desirable to have an improved latch for a disk drive, that is light weight and small that reliably secures a drive arm in a parking position and prevents it from being dislodged from the parking position when the disk drive is subjected to a shock or blow.
It is an object of one aspect of some preferred embodiments of the present invention to provide an improved latch for locking a drive arm of a disk drive in a parking position that is small and light weight.
It is an object of another aspect of some preferred embodiments of the present invention to provide a latch that has a locking action that is substantially unaffected by a blow or shock delivered to a disk drive in which the latch is installed.
According to another aspect of some preferred embodiments of the present invention, the latch has a locking action that is substantially unaffected by the direction of a blow or shock delivered to the disk drive.
According to another aspect of some preferred embodiments of the present invention the latch does not require a drive arm motor of the drive arm to provide force in order to release the locking action of the latch.
An object of yet another aspect of some preferred embodiments of the present invention is to provide a latch that does not produce a magnetic field that interferes with the operation of a disk drive in which the latch is installed.
Another aspect of some preferred embodiments of the present invention provides a latch, for locking a drive arm in a parking position, that has low power consumption and consumes power only when the drive arm is released from the locking position.
It is an object of yet another aspect of some preferred embodiments of the present invention to provide a latch operated by a piezoelectric micromotor.
A latch for locking a drive arm of a disk drive in a parking position, in accordance with a preferred embodiment of the present invention, comprises a latch stop and a latch hook.
The latch stop comprises a baffle that is moveable between an open and closed position. The latch hook is preferably mounted to the drive arm near or at the end of the drive arm distant from the data head. The latch hook moves with the drive arm and the latch hook and the baffle are so positioned that when the baffle is in the closed position the baffle protrudes into the path of motion traced out by the latch hook as the drive arm moves. As a result, when the baffle is in the closed position the latch hook cannot move from one side to the other side of the baffle without the latch hook colliding with the baffle. The baffle is normally in the closed position.
When the drive arm is in operation, the data head of the drive arm is over a data region of the data disk that is being read or written by the data head and the latch hook is on a first side, hereinafter referred to as an xe2x80x9coperating sidexe2x80x9d, of the baffle. When the drive arm is in the parking position, the data head is over a region, a xe2x80x9cparking regionxe2x80x9d, of the data disk that is not used to store data and the latch hook is on a second side, hereinafter referred to as a xe2x80x9cparking sidexe2x80x9d, of the baffle.
The latch hook and baffle are constructed so that the latch hook can move from the operating side of the baffle to the parking side of the baffle when the baffle is in the closed position but cannot move from the parking side to the operating side of the baffle when the baffle is in the closed position.
Preferably, the latch hook is resiliently biased in a locking orientation. If the latch hook collides with the baffle from the parking side of the baffle, the latch hook is not displaced from the locking orientation and, the baffle blocks and stops the motion of the latch hook towards the operating side of the baffle. If the latch hook collides with the baffle from the operating side of the baffle, the latch hook displaces resiliently from the locking orientation so that the latch hook can pass to the parking side of the baffle. After the latch hook has passed to the parking side of the baffle, the latch hook snaps back to the locking orientation and cannot return to the operating side of the baffle unless the baffle is moved to the open position. The drive arm is thereby locked in the parking position.
The latch stop is moved back and forth between the open and closed positions by a piezoelectric motor. A small light weight piezoelectric motor suitable for moving a latch stop, in accordance with a preferred embodiment of the present invention, is described in the following documents which are incorporated herein by reference: U.S. Pat. Nos. 5,453,653, 5,616,980, 5,682,076, 5,714,833; EPO publication EP 0,755,054; Israel Patent 109,399; Israel Patent Applications 110,155, and 114,656 by some of the same applicants as the applicants of the present application; and PCT Application PCT/IL/98/00046 by some of the same applicants as the applicants of the present application. In some latches, in accordance with a preferred embodiment of the present invention, the piezoelectric motor is coupled directly to the body of the baffle in order to move the baffle between open and closed positions. In other preferred embodiments of the present invention the baffle is connected to the piezoelectric motor via a transmission. The piezoelectric motor is coupled to the transmission and xe2x80x9cdrivesxe2x80x9d the transmission in order to move the baffle between open and closed positions.
There is therefore provided in accordance with a preferred embodiment of the present invention a latch for a drive arm of a disk drive, wherein the drive arm has a parking position and an operating position and wherein the latch is operable to lock the drive arm in the parking position comprising: a latch stop comprising a baffle moveable between an open position and a closed position; and a piezoelectric motor operable to move the baffle between the open and closed positions, wherein the drive arm, in the parking position, engages the baffle and is prevented from leaving the parking position, when the baffle is in the closed position and is not prevented from leaving the parking position when the baffle is in the open position.
Preferably, the drive arm comprises a latch hook and when the drive arm is in the parking position and the baffle is in the closed position the latch hook engages the baffle and the drive arm is prevented from leaving the parking position, and when the baffle is in the open position the drive arm is not prevented from leaving the parking position.
Preferably, the baffle is resiliently biased in the closed position and as the drive arm moves from the operating position to the parking position the latch hook displaces the baffle from the closed position and when the drive arm reaches the parking position the baffle snaps back to the closed position.
Alternatively or additionally the latch hook is preferably resiliently biased in a locking orientation and as the drive arm moves from the operating position to the parking position the baffle displaces the latch hook from the locking orientation and when the drive arm reaches the parking position the latch hook snaps back to the locking orientation.
Alternatively or additionally, the baffle preferably comprises a coupling surface and the piezoelectric motor is resiliently pressed to the coupling surface and when the piezoelectric motor is activated, vibratory motion of the piezoelectric motor moves the baffle between open and closed positions.
In some preferred embodiments of the present invention the latch stop comprises a transmission having a coupling surface against which the piezoelectric motor is resiliently pressed, and the baffle is mounted to the transmission so that motion of the transmission moves the baffle between open and closed positions when the piezoelectric motor is activated.
Preferably, the transmission comprises a baffle arm and the baffle is mounted to the baffle arm.
The motion of the transmission preferably causes the baffle arm to rotate around a baffle arm axis to move the baffle between open and closed positions.
Preferably, the transmission comprises a coupling arm and the coupling surface is a surface of the coupling arm, and vibratory motion of the piezoelectric motor causes the coupling arm to rotate about a coupling arm axis which causes the baffle arm to rotate around the baffle arm axis.
The baffle arm axis and the coupling arm axis preferably coincide.
In some preferred embodiments of the present invention the coupling surface is a surface of the baffle arm and the baffle arm comprises a resilient stem having a fixed end, which resilient stem presses the coupling surface to the piezoelectric motor, and vibratory motion of the piezoelectric motor causes the coupling arm to rotate about the fixed end to move the baffle between open and closed positions.
Preferably the coupling surface is clad with a wear resistant material. Preferably, the piezoelectric motor comprises a friction nub and when the piezoelectric motor and the coupling surface are pressed together the friction nub contacts the coupling surface.
There is also provided a method of locking a drive of a disk drive in a parking position using a baffle having an open and a closed position, wherein when the drive arm is in the parking position and the baffle is in the closed position the drive arm engages the baffle and the drive arm is locked in the parking position, and when the baffle is in the open position the drive arm is free to leave the parking position, and moving the baffle between the open and closed positions using a piezoelectric motor,
The invention will be more clearly understood by reference to the following description of preferred embodiments thereof read in conjunction with the figures attached hereto. In the figures identical structures, elements or parts which appear in more than one figure are labeled with the same numeral in all the figures in which they appear. The figures are listed below and: